The present invention relates to solid inorganic glasses containing hydrocarbon compounds, and is based on the discovery of a family of hybrid (organic/inorganic) glasses wherein significant amounts of certain polycylic aromatic hydrocarbon compounds can be successfully dissolved in the glass.
The class of polycyclic or polynuclear aromatic hydrocarbons includes a number of compounds exhibiting photophysical responses to light. Such responses include lasing, luminescence (phosphorescence and fluorescence), and also triplet state absorption. These so-called photosensitive compounds may contain as few as fourteen carbon atoms (eg. phenanthrene C.sub.14 H.sub.10) or up to nearly fifty carbon atoms (eg. rubrene C.sub.42 H.sub.28).
Compounds of this class include the well known triplet state compounds or triplet state dyes. Triplet state compounds have been dispersed in plastic matrix materials to provide light-responsive products such as photochromic plastics. U.S. Pat. No. 3,635,544 discloses photochromic plastics containing triplet state aromatic hydrocarbons.
Light-responsive combinations comprising a polymeric matrix and a dissolved polycyclic hydrocarbon such as a triplet state dye compound offer rapid darkening in response to actinic radiation and rapid relaxation in the absence thereof. However, plastic polymer matrix materials typically exhibit only limited hardness and in addition are permeable to oxygen and other constituents which can adversely affect the photophysical response characteristics of the triplet state compound dissolved therein.
The use of a glassy matrix to study luminescence in triplet state compounds is proposed by M. Kasha, Jour. Opt. Soc. Am. 38 (12) pages 1068-73 (December 1948). Kasha employed a boric acid glass, but notes that other easily-fusible glassy materials such as aluminum sulfate, sugars, boroglycerides, mixtures of sodium borate and sodium metaphosphate, and mixtures of silicates and phosphates, might be suitable. While such glassy materials offer the advantage of reduced oxygen permeability, their chemical durability is low. Thus they have been employed only as vehicles for study, rather than as practical media for supporting the photophysical characteristics of dissolved hydrocarbons.
Another group of photosensitive polycyclic aromatic hydrocarbons or dye compounds exhibiting light responsive characteristics are the so-called laser dyes. As noted by J. M. Kauffman in Applied Optics, 19 (20) 3431-3435 (October 1980) many polycyclic aromatic hydrocarbons are known to exhibit lasing responses when stimulated with light under appropriate conditions.
Yet another group of aromatic dye compounds has been identified wherein the compounds exhibit changes in light absorption in response to the application of an electric field, ie., an electrochromic response. These field-responsive compounds are exemplified by the so-called viologens, which are typically 4-4'-dipyridinium derivatives (C. J. Schoot et al., Appl. Phys. Lett. 23 [2] 64-65 [July 1973]).
In the case of the lasing and electrochromic dyes, host materials have generally been limited to plastics, or to organic or aqueous solvents. Thus practical applications utilizing the light- or electric-field-responsive characteristics of these hydrocarbons have been somewhat limited.
It is therefore a principal object of the present invention to provide novel combinations of polycyclic aromatic hydrocarbon compounds and glass wherein the glass provides a matrix of improved durability and utility.
It is a further object of the invention to provide a hybrid or composite organic/glass material wherein the photophysical response characteristics of dissolved organic compounds can be usefully exploited.
Other objects and advantages of the invention will become apparent from the following description.